(57) Disclosed is a method for charging a battery and circuitry for performing the method.
The method includes steps of: (a) generating a charging current (Ich) for a battery;
(b) generating a replica current (Irep) of Ich, where Irep=Ich/N, where N > 1; (c)
measuring a voltage drop induced by Irep across a measurement resistance; and (d)
using the measured voltage drop for controlling a magnitude of Ich. Preferably N is
greater than about 10, more preferably N is greater than about 100, and in the most
preferred embodiment N is in a range of about 100 to about 1000. The step of generating
the charging current (Ich) includes a step of operating a first device having an input
node coupled to a source of charging current, the step of generating the replica current
(Irep) includes a step of operating a second device having an input node coupled to
the source of charging current; wherein the first device and the second device are
both driven with the same control signal. The control signal may be a pulse width
modulated signal having a pulse width that is controlled as a function of the measured
voltage drop across the measurement resistance, or a DC voltage having an adjustable
voltage value. In the preferred embodiment the step of generating the replica current
(Irep) includes a step of operating a servo loop to force a potential appearing at
an output node of the second device to equal a potential appearing at an output node
of the first device. A battery discharge measurement circuit is also disclosed, and
operates in accordance with the same principles as the battery charging circuit.
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